The present invention relates to a molding apparatus and a method for using the molding apparatus.
In a typical automobile, the knobs of various switches having various functions are provided on the armrest of side doors. Even in the same type of vehicles, the number of the knobs varies according to the grade of each vehicle and to the sales channels. For example, in one grade of a vehicle, a certain knob is provided in the cover of the armrest, and in another grade, the knob is not provided. In this case, two types of covers are prepared. The cover of one type has a through hole for the knob, and the knob protrudes through the hole. The cover of the other type has no through hole for the knob, and the part that corresponds to the knob is closed. The type of the armrest cover is selected according to the grade of the vehicle so that substantially identical type of armrest can be used for both of a vehicle that has the knob and a vehicle that does not have the knob.
A typical molding apparatus and a method for using the molding apparatus for molding such covers are described below with reference to FIGS. 11 to 14(b).
As shown in FIGS. 11 and 12(a), the molding apparatus includes a stationary die 51 and a movable die 52. The molding apparatus is used for molding a first cover 56, which has a predetermined through hole, and a second cover 58, which does not have the predetermined through hole.
When molding the first cover 56, a first core 53 is used. When molding the second cover 58, a second core 54 is used.
A core receiving section 55, which is a recess, is formed in the stationary die 51. The cores 53 and 54 are selectively received by the core receiving section 55. When molding the first cover 56, which has the through hole, the first core 53 is located in the core receiving section 55 as shown in FIG. 11. The first core 53 is formed such that its distal surface 53a contacts the movable die 52.
In this state, a first cavity 57 is defined by the stationary die 51, a movable die 52, and the first core 53. The first cavity 57 is filled with a synthetic resin for molding the first cover 56.
When molding the second cover 58, which does not have the through hole, the second core 54 is provided in the core receiving section 55 as shown in FIG. 12(a). The second core 54 is formed such that the distal surface 54a is flush with an exterior forming surface 51a of the stationary die 51.
In this state, a second cavity 59 is defined by the stationary die 51, the moveable die 52, and the second core 54. The second cavity 59 is filled with a synthetic resin for molding the second cover 58. The surfaces of the covers 56, 58 that are fanned by the stationary die 51 are exterior surfaces 56a, 58a, which are seen by a driver and passengers of the vehicle.
The second cover 58, which is molded with the second core 54, has the following drawbacks. The exterior surface 58a of the second cover 58 is defined by the distal surface 54a of the second core 54 and the exterior forming surface 51a of the stationary die 51. Therefore, due to a small space created between the second core 54 and the stationary die 51 (the core receiving section 55), a square line 60 formed on the exterior surface 58a at a position corresponding to the periphery of the core 54. The second cover 58, which has the line 60, is hardly welcome by users. Therefore, there has been a demand for a cover having no line 60.
Accordingly, to make the line 60 less conspicuous, the following method has been known in the art.
In this method, a third core 61 is located in the core receiving section 55 as shown in FIG. 13(a). The third core 61 has a bulge 62 protruding from the periphery of the end surface 61a toward the movable die 52. The distal surface 61a of the third core 61, which is surrounded by the bulge 62, is located in a common plane with the exterior forming surface 51a of the stationary die 51. A cover molded by using the third core 61 will be referred to as a third cover 63.
A cavity 64 is defined by the stationary die 51, the movable die 52, and the third core 61. The cavity 64 is filled with synthetic resin for molding the third cover 63. As shown in FIG. 13(b), a groove 65 is formed on the exterior 63a of the third cover 63 by the bulge 62.
As a result, the line 60 (see FIGS. 12(a) and 12(b)) are not formed. Instead, the groove 65 is positively formed in the third cover 63 by the bulge 62 of the third core 61. The third cover 63 is therefore welcome by users.
However, since the bulge 62 is formed along the periphery of the third core 61, the stationary die 51 (the core receiving section 55) and the bulge 62 define a right angle as shown in FIG. 14(a). Therefore, the outer periphery of the groove 65 has an orthogonal cross-section. Further, if there is a space between the third core 61 and the stationary die 51 (the core receiving section 55), flash is formed at the periphery 66.
As a result, when a user touches the exterior surface 63a of the third cover 63 with fingers, the fingers get snagged at the periphery 66, which disturbs the user.
To reduce the discomfort experienced by users, a molding apparatus shown in FIG. 14(b) may be used. In this apparatus, the cross-section of the bulge 62 at the part contacting the stationary die 51 (the core receiving section 55) is formed arcuate so that the periphery 66 of the groove 65 is chamfered.
In this case, however, the bulge 62 is not formed along the periphery of the third core 61. Therefore, a side 62a of the bulge 62 that corresponds to the stationary die 51 is not flush with a surface 61b of the third core 61 that contacts the stationary die 51 (the core receiving section 55). This again forms a line 60 on the exterior surface 63a of the third cover about the groove 65.